Automatic circuit breaker



Jan. 14, 1964 w BRACKET-r 3,118,034

AUTOMATIC CIRCUIT BREAKER United States Patent Otice 3,118,034 PatentedJan. 14, 1964 3,118,034 AUTMATIC CHRCUH BREAKER Lawrence W. llraclrett,Georgetown, Mass., assigner to Wood Electric Corporation, Lynn, Mass., acorporation of Massachusetts Filed Sept. 30, 1960, Ser. No. 59,561 2Claims. (Cl. 26d- 116) The eld of this invention is that of circuitbreakers, and the invention relates more particularly to circuitbreakers of the non-trip free type.

Circuit breakers of the trip-free and non-trip free type have previouslybeen well known in the circuit breaker art. However, whereas trip-freecircuit breakers have been adapted to open circuits rapidly andautomatically in response to high, instantaneous current overloads,circuit breakers of the non-trip free type have generally been confinedto relatively low current application wherein manual holding of thebreaker in closed circuit, or nontrip free, position would not causeinjury to the breaker and have accordingly not been adapted to opencircuits rapidly. Nevertheless certain circuit breaker applications,such as breakers used in aircraft control circuits, require that abreaker be adapted not only to open rapidly and automatically forprotecting a circuit against high instantaneous current overloadswithout injury to the breaker but also to be held in non-trip freeposition for short periods with corresponding durability.

Objects of this invention are to provide a non-trip free circuit breakerwhich is adapted to open rapidly and automatically; to provide anon-trip free circuit breaker which is adapted to open automatically inresponse to relatively high instantaneous current overload withoutinjury to the circuit breaker, which can be manually held in closedcircuit or non-trip tree position when conditioned by current overload,and which is adapted to open a circuit rapidly upon release fromnon-trip free position while conditioned by current overload.

The substance of the invention can be briey summarized as tocharacteristic aspects thereof as follows.

Circuit breakers according to the invention comprise in a principalaspect, fixed contact means, movable contact means cooperable therewithfor closing a breaker circuit, a pair of pivotally mounted cam members,one of which is adapted to move the movable contact means between openand closed circuit positions, and means biasing the cam means together.Latch means engage the other of the cam members and are adapted torelease engagement of said member in response to overload current in thebreaker circuit. An operating member movable between open and closedcircuit positions carries wedging means which are adapted to be movedbetween the cam members for moving said one cam member between open andclosed circuit positions in response to movement of the operating memberwhen the other cam member is engaged by the latch means, and which areadapted to be automatically released from between the cam members forpermitting the cam biasing means to move said one cam member to opencircuit position when said other cam member is released from latchengagement in response to overload current in the breaker circuit.According to this invention, means are carried by the operating memberwhich are engageable with said one cam member, whereby manual holding ofthe operating member in closed circuit position will hold the one cammember in closed circuit position independently of latch engagement ofsaid other cam member.

In a preferred embodiment of this invention, a pair of cams and amovable Contact member are pivotally mounted on a common pivot, andmeans are provided for biasing the contact member away from one of saidcam members and for limiting the extent of separation of the Contactmember and said cam. In this construction the operating member hasWedging rolls pivotally suspended therefrom which are adapted to bemoved between the cams for manually opening and closing the breakercircuit in response to movement of the operating member when the otherof the cams is latched and which are adapted to be releasedautomatically from between the cams when said other cam is released fromlatch engagement in response to overload current in the breaker circuit.A slide carried by the operating member is guided by sliding engagementwith the cam pivot and has a portion engageable with said one cam bymeans of which, when the operating member is manually held in closedcircuit position, said one cam member is held in closed circuit positionindependently of latch engagement with said other cam.

rl`hese and other objects and aspects of the invention will appear fromthe following description of a preferred embodiment thereof illustratingits novel characteristics.

The description refers to drawings in which:

FIG. 1 is a section View taken on vertical axis of the circuit breakershowing the breaker in closed circuit position;

HG. 2 is a section view similar to FIG. l showing the circuit breaker inopen circuit position;

FIG. 3 is a section view similar to FIG. l showing the circuit breakerin non-trip free position;

FIG. 4 is a section view taken along lines 4 4 of FIG.

FiG. 5 is a perspective View of a cam incorporated in this circuitbreaker; and

PEG. 6 is a perspective View of a second cam incorporated in thiscircuit breaker.

Referring to the drawing, l@ indicates a circuit breaker casing whichencloses the breaker operating mechanism i12. The casing comprises asubstantially rectangular open-ended box lle, of insulating materialsuch as glasslled asbestos, and is provided with a metallic cover 16which is secured thereto by means of rivet 16.1 and which is preferablyinsulated from the breaker operating mechanism by an insulating piece16.2. internally-threaded bushings 13 are pres-tted within casing coverapertures in conventional manner and serve for mounting the circuitbreaker on an instrument panel. The casing cover also has a neck 2@ inwhich an operating member 22, preferably of insulating material, isslidably mounted.

The circuit breaker terminals 26 and 2S preferably have terminal screws26.1 and 28.1 for facilitating electrical connection thereto. Theterminal 2o, which is of short length, is secured within the casing bymeans of rivet 2.6.2 and carries a fixed contact 27, whereas theterminal 2S extends within the casing along one casing side and has abifurcated end 23.2 tted within a recess 143.1 formed in the casing sidewall. Preferably an insulating tube 28.3 disposed between the bifurcatedends of the terminal 28 provides electrical clearance between theterminal and the adjacent mounting bushing llti. Terminal mountingscrews Zi extend through the casing side wall and threadedly engage theterminal 28 for a purpose to be described below.

Within the casing there is a pivot pin 30 which its within casingapertures 36.1, 30.2 and preferably is secured therein and electricallyinsulated with a potting material such as an epoxy resin as indicated at39.3. A movable contact member 32 is pivotally mounted on the pin 3b bymeans of a rolled end 321 and carries the Contact 33 which is cooperablewith the fined contact 27 for closing the breaker circuit. A cam member34 having a rolled end 34M is similarly mounted on the pin 30 and isbiased away from the movable contact member 32 by means of a helicalcoil spring 35. Cam member 34 has an extension arm 34.2 which is adaptedto be engaged with the lip 32.2 of the movable Contact member forlimiting separation of the cam member and the contact member 32. The cammember is provided with the cam surface .34.3 and has horizontallyextending portions which also serve as cam surfaces. A cam member 36,which is also mounted for rotation on the pin 3d as shown in FIG. 6, isprovided with ears 36.1 slotted as at 36.2 to receive the pivot pin 36and has a cam surface 36.3 recessed at 36.4. This cam member also has ashoulder 36.5 for a purpose to be described below. The cam members 34and 36 are biased together by springs 39 and 49 respectively, eachspring being secured between a respective cam member as at 34.5 and 36.6respectively and pins 4l mounted in slots 41.1 in the casing walls.

A link 42 is secured at each side of the operating member 22 by means ofthe pivot pin 42.1, and between the links there are three wedging rolls,including two outer rolls 44.1 and an inner roll 44.2, coaxially mountedon pivot pin 44.3. The rolls 44d and 44.2 are adapted to engage the camsurfaces 34.3 and 36.3 respectively.

A bimetallic latch member 46 of substantially U- shape is secured to theterminal 28 by conventional means such as soldering or brazing andcarries the latch plate 46.1, secured thereto by means of rivets 46.2,which is adapted to engage the shoulder 36.5 of the cam member 36.Preferably but not necessmily the terminal mounting screw 23.4 maysupport a magnet core 4S which is insulated from the terminal 28 and themounting screw 28.4 by an insulating piece 453.1 and an insulatingbushing 43.2 respectively. The magnet core, if provided, is cooperablewith the magnet armature 43.3 attached t the bimetallic member 46. Asthus constructed the degree of latch plate engagement with the shoulder36.5 can be conveniently adjusted by means of the screws 28.4 afterbreaker assembly and the screws can then be electrically insulated witha potting material as at 28.5.

A flexible braid 49 soldered to the bimetallic member 46 and the movablecontact members 32 completes the breaker circuit. The breaker circuitthen extends from the terminal 2S through the bimetallic latch member46, flexible braid 49, the movable contact member 32, the contacts 33and 27 to the terminal 26.

The pivot pin 42.1 carried by the operating member 42 also supports theslide member Sil for movement with the operating member. The slidemember includes the slotted end portion Sill which slidably engages thecam and contact member pivot 30 for guiding movement of the slide inresponse to movement of the operating member and is provided with a camsurface 56.2 adapted to be slidingly engaged with the cam surfaceextensions 34.4 ot the cam member 34.

FIG. 2 illustrates the open circuit position of the circuit breakerprovided by this invention showing the operating member in fullyextended position and the contact arm 32 separated from the cam member34 to its fullest extent. In this construction, downward movement of theoperating member advances the wedging rolls 44.1 and 44.2 between thecam members 34 and 36. Since the shoulder 36.5 of the cam member 36 isnormally engaged by the latch plate 46.1 and cannot be rotated, the cammember 34 will be rotated in a counterclockwise direction whereby thecontact member 32 is similarly rotated in a counterclockwise directionfor closing the breaker circuit. Further downward movement in theoperating member 22 snaps the wedging roll 44.2 within the cam recess36.4 further rotating the cam member 34 for resiliently loading thebreaker contacts through the spring and for locking the wedging rollsbetween the cam members. This position of the circuit breaker isillustrated in FIG. 1.

The circuit breaker can be moved from the closed p0- sition shown inFIG. 1 to the open circuit position shown in FIG. 2 by manuallywithdrawing the operating mem- 75 ber 22, and therefore the wedgingrolls 44.1 and 44.2, from between the cam members. When this occurs, thesprings 39 and 4d biasing the cam members 34 and 36 together return thecam member 34 to the original position shown in FlG. 2 whereby the camextension arm 34.2 rapidly snaps the movable contact member 32 to opencircuit position.

Alternatively when the circuit breaker is in the closed circuit positionshown in FlG. 1 the circuit breaker iS automatically operable to bemoved to open circuit position in response to current overload in thebreaker circuit. Overload current in the breaker circuit, by heating thebimetallic member 46, causes ilexing of said member and releasesengagement of the cam shoulder 36.5 by the latch plate 461. When thisoccurs, the cam member 36 is permitted to rotate in a clockwisedirection releasing the wedging rolls 44.1. and 44.2 from between thecam members whereupon the springs 3S and 49 cooperate to return the cammembers to original position and also litt the operating member to itsfully extended, open circuit, position. lf the overload current in thebreaker circuit is relatively high, even if for very short duration, amagnetic field will be established within the magnet core 48 whereby themagnet armature 48.3 will be attracted thereto, similarly flexing thebimetallic member and releasing latch engagement of the cam shoulder36.5. lt can be seen that the circuit breaker provided by this inventionis adapted to open the breaker circuit automatically in response tocurrent overload in the circuit, and that, whether current overloadoccurring with* in the circuit comprises a relatively low overload oflong duration or a relatively high overload of short duration, thebreaker contacts will be separated with such rapidity that the breakerwill escape substantial injury.

However even though bimetallic latch member 46 is conditioned by acurrent overload, either of relatively low or relatively high degree,the operating member 22 can be manually held in depressed,closed-circuit position whereby the slide S6 slidably engages the cammember 34 for moving said cam member to closed circuit position, asshown in FIG. 3. Similarly upon release of the operating member 22 fromits non-trip free position, the Springs 38 and 4d will return the cammembers 34 and 36 to the original position as shown in FlG. 2 forsnapping the contact member 32 to open circuit position.

While the preferred embodiment of this invention has been illustrated,it should be understood that this invention includes all modiiicationsand equivalents which fall within the scope of the appended claims.

I claim:

l. A circuit breaker comprising an insulating casing, a Contact fixedwithin the casing, a pivot pin mounted within the casing, a pair of camspivotally mounted on said pin, a movable contact member cooperable withthe fixed contact for closing a circuit, said member being connectedwith one of said cams for movement with said cam between open and closedmount positions, means biasing the cams together, latch means normallyengaging the other of said cams and adapted to release engagement ofsaid cam in response to overload current in the breaker circuit, anoperating member slidably mounted in the casing for movement betweenopen and closed circuit positions, and wedging means pivotally connectedto the operating member and adapted to be wedged between the cams inresponse to movement of the operating member for moving said one cambetween open and closed circuit positions when said other cam is engagedby the latch means, said wedging means being automatically released frombetween the cams for permitting said biasing means to move said one camand said operating member to open circuit position when said other camis released from latch engagement, in combination with an additionalmember carried by the operating member and slidingly engaged with saidpivot pin, said additional member having a projection engageable withsaid one cam,

whereby the operating member can be manually held in closed circuitposition for holding said one cam member in closed circuit positionindependent of latch engagement with said other cam member.

2. A circuit breaker comprising an insulating casing, a contact xedwithin the casing, a pivot pin mounted within the casing, a pair of camspivotally mounted on said pin, a movable contact member cooperable withthe fixed Contact for closing a circuit, means biasing the contactmember away from one of said cams, means limiting separation of said onecam and contact member, a bimetallic latch normally engaging the otherof said cams, said latch being interposed in the breaker circuit andbeing adapted to ilex in response to relatively low overload current inthe circuit thereby to release engagement of said cam, a magnet armaturecarried by the bimetallic latch, electromagnet means adapted to beactuated by relatively high overload current in the breaker circuit forattracting said armature to flex said bimetallic member, an operatingmember slidably mounted in the casing for movement between open andclosed circuit positions, wedging rolls suspended from the operatingmember for movement therewith, said rolls being adapted to be wedgedbetween the cams for moving said one cam to load said contact memberresiliently in closed circuit position and to be drawn from between thecams for permitting said Contact member and cam biasing means to snapthe contact member to open circuit position when said other cam islatched, said rolls being automatically released from between said camsfor permitting said biasing means to snap said one cam and operatingmember to open circuit position when said other cam is released fromlatch engagement, and a slide member carried by said operating memberand guided by sliding engagement with said pivot pin, said slide havinga surface engageable with said one cam whereby when said operatingmember is manually held in closed circuit position said one cam will beheld in closed circuit position independently of latch engagement ofsaid other cam.

References Cited in the iile of this patent UNITED STATES PATENTS2,287,875 Grober June 20, 1942 2,409,917 Von Hoorn Oct. 22, 19462,613,296 Wood Oct. 7, 1952 2,813,168 Mascioli et al Nov. 12, 1957

1. A CIRCUIT BREAKER COMPRISING AN INSULATING CASING, A CONTACT FIXEDWITHIN THE CASING, A PIVOT PIN MOUNTED WITHIN THE CASING, A PAIR OF CAMSPIVOTALLY MOUNTED ON SAID PIN, A MOVABLE CONTACT MEMBER COOPERABLE WITHTHE FIXED CONTACT FOR CLOSING A CIRCUIT, SAID MEMBER BEING CONNECTEDWITH ONE OF SAID CAMS FOR MOVEMENT WITH SAID CAM BETWEEN OPEN AND CLOSEDMOUNT POSITIONS, MEANS BIASING THE CAMS TOGETHER, LATCH MEANS NORMALLYENGAGING THE OTHER OF SAID CAMS AND ADAPTED TO RELEASE ENGAGEMENT OFSAID CAM IN RESPONSE TO OVERLOAD CURRENT IN THE BREAKER CIRCUIT, ANOPERATING MEMBER SLIDABLY MOUNTED IN THE CASING FOR MOVEMENT BETWEENOPEN AND CLOSED CIRCUIT POSITIONS, AND WEDGING MEANS PIVOTALLY CONNECTEDTO THE OPERATING MEMBER AND ADAPTED TO BE WEDGED BETWEEN THE CAMS INRESPONSE TO MOVEMENT OF THE OPERATING MEMBER FOR MOVING SAID ONE CAMBETWEEN OPEN AND CLOSED CIRCUIT POSITIONS WHEN SAID OTHER CAM IS ENGAGEDBY THE LATCH MEANS, SAID WEDGING MEANS BEING AUTOMATICALLY RELEASED FROMBETWEEN THE CAMS FOR PERMITTING SAID BIASING MEANS TO MOVE SAID ONE CAMAND SAID OPERATING MEMBER TO OPEN CIRCUIT POSITION WHEN SAID OTHER CAMIS RELEASED FROM LATCH ENGAGEMENT, IN COMBINATION WITH AN ADDITIONALMEMBER CARRIED BY THE OPERATING MEMBER AND SLIDINGLY ENGAGED WITH SAIDPIVOT PIN, SAID ADDITIONAL MEMBER HAVING A PROJECTION ENGAGEABLE WITHSAID ONE CAM, WHEREBY THE OPERATING MEMBER CAN BE MANUALLY HELD INCLOSED CIRCUIT POSITION FOR HOLDING SAID ONE CAM MEMBER IN CLOSEDCIRCUIT POSITION INDEPENDENT OF LATCH ENGAGEMENT WITH SAID OTHER CAMMEMBER.